NEUTRALIZATION TESTS FOR DENGUE AND JAPANESE ENCEPHALITIS VIRUSES BY THE FOCUS REDUCTION METHOD USING PEROXIDASE-ANTI-PEROXIDASE STAINING

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 21  (4) , 137-147
Abstract
Neutralization tests were made on 4 types of dengue (DEN) virus and Japanese encephalitis (JE) virus by incubation of serially diluted [rabbit] antisera and constant amounts of the viruses and focus assay of surviving virus infectivity with peroxidase-anti-peroxidase (PAP) staining. Neutralization reactions were virtually completed in 2 h on incubation of serum-virus mixtures at 28.degree. C. A straight regression line was obtained on a probit chart by plotting the focus reduction rates at various dilutions of a given serum against the log of the serum dilution used in the test. The slopes of the probit regression lines for the neutralization for DEN types 1 and 3 were similar, but differed somewhat from those for DEN type 2 and type 4. The slope of the line for JE virus was quite different from those for DEN viruses. The 50% focus reduction titer (FR50) of neutralizing antibodies of a given serum could be estimated from the focus reduction rates at several dilutions of the test serum when the latter was between 25-75% of the value of the control.